Deformable TPE Stopper Cavity for Low Break Loose Force
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Solution Overview
Problem
Existing injectors face challenges with high break loose force (BLF) due to the 'stick effect' of sealing elements with the inner wall, especially in prefilled syringes, which can lead to increased friction and adverse effects like silicone droplets being injected into patients, particularly in ophthalmic injections, and is exacerbated by temperature and humidity, necessitating lubrication that can be harmful in certain drug formulations.
Innovation Solution
A stopper design featuring a deformable sealing element made of thermoplastic elastomer (TPE) with a cavity larger than the access diameter, positioned to overlap with the sealing element, reducing the break loose force without the need for external lubricants, ensuring container closure integrity and smooth user experience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If silicone lubrication is used to reduce friction and enable easy piston movement, then glide force is reduced and piston movement becomes smooth, but proteins in pharmaceutical compositions aggregate and silicone particles are injected into patients causing harmful effects
Solution Approach 1:
The patent removes the harmful silicone lubrication from the system entirely. Instead of using silicone-coated pistons or lubricated inner walls, the invention employs a dry friction reduction mechanism through the deformable sealing element that maintains sealing while minimizing contact friction, thereby eliminating protein aggregation and silicone particle contamination risks
Solution Approach 2:
The deformable sealing element acts as an intermediary between the piston and the inner wall. This sealing element made of thermoplastic elastomer provides the necessary sealing function while its deformable nature allows it to accommodate surface irregularities, reducing the need for high friction forces and eliminating the need for harmful silicone lubrication
2Reliability
If the sealing element interacts with the inner wall to maintain sealing, then container closure integrity is ensured, but static friction increases causing high break loose force
Solution Approach 1:
The sealing element is designed to be dynamically deformable rather than rigid. Made of thermoplastic elastomer, it can adapt its shape during piston movement, maintaining continuous contact with the inner wall for sealing while its elasticity reduces static friction buildup, thereby lowering break loose force without compromising container closure integrity
Solution Approach 2:
The patent changes the material parameters of the sealing element from traditional rigid or silicone-based materials to thermoplastic elastomer with specific viscoelastic properties. This material parameter change allows the sealing element to maintain sealing pressure while reducing coefficient of friction, thus lowering break loose force while ensuring reliable container closure
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The stopper design significantly reduces static and dynamic forces, allowing for easier injection without lubrication, maintaining container closure integrity and preventing adverse effects on pharmaceutical compositions, particularly beneficial for long-term storage and use in prefilled injectors.
Implementation Method 1
A stopper design featuring a deformable sealing element made of thermoplastic elastomer (TPE)
Data Source
AI summary
The present invention relates to a stopper for an injector for delivery of a pharmaceutical composition and to an injector with the stopper. The stopper has a stopper body with an actuating surface opposite an outlet surface, an axial length between the actuating surface and the outlet surface, and a transverse diameter, which stopper body defines an access diameter, the stopper at an axial location from the actuating surface comprising a deformable sealing element surrounding the stopper body and having an outer diameter, which is larger than the transverse diameter, which deformable sealing element is made from a thermoplastic elastomer and has an axial extension in the range of 5% and 95% of the axial length of the stopper body, and the stopper comprising a cavity at the axial location of the deformable sealing element, the cavity having a lateral extension larger than the access diameter of the stopper body.